Field of the Invention
The present invention relates to an optical scanning apparatus, and to an optical scanning apparatus effectively usable together with an image forming apparatus, such as a laser beam printer (LBP), a digital copying machine, and a multifunction printer (a printer equipped with multiple functions).
Description of the Related Art
There is known an optical scanning apparatus including an incident optical system, which guides a light flux emitted from a light source to a deflector, and an imaging optical system, which guides the light flux deflected by the deflector to a surface to be scanned, as an optical scanning apparatus for use in an image forming apparatus. Japanese Patent Application Laid-Open No. 2015-31824 discusses an optical scanning apparatus configured in such a manner that the imaging optical system is disposed closer to the deflector, which contributes to reductions in a length of the imaging optical system in a main-scanning direction and a length of the entire apparatus in an optical-axis direction, thus realizing reductions in a size and cost.
Now, the image forming apparatus requires an area for placing other members, such as a toner container, whereby it is difficult to reduce a distance between the imaging optical system and the surface to be scanned. Therefore, reducing the distance between the deflector and the imaging optical system, like the configuration discussed in Japanese Patent Application Laid-Open No. 2015-31824, leads to a necessity of increasing a lateral magnification of the imaging optical system in a sub-scanning cross-section (a sub-scanning magnification). Therefore, this configuration ends up increasing a sensitivity of the optical performance to a variation in the imaging optical system at the time of the formation thereof. That is, the configuration increases the amount of a change in optical performance according to a variation in the imaging optical system at the time of manufacture, and an assembly error in each member such as the light source.
In this case, one possible method for solving this problem is to reduce a sub-scanning magnification of the incident optical system to thereby reduce a sub-scanning magnification of the entire optical system, thus preventing or reducing the increase in the sensitivity of the optical performance. However, simply increasing a distance between the light source and the incident optical system to achieve that leads to a necessity of enlarging the incident optical system in the sub-scanning direction, making it difficult to reduce a size of the incident optical system.